These sentences are from my test in which I answered these sentences incorrectly. So please suggest the right answers to them.

1)Ram said to me,"I go to school daily."(change to indirect speech)
2)He wrote me a letter.(change to passive voice)
3)Who built the Taj?(change to passive voice)
4)when we (feel) safe,we stopped to rest.
5)The judge was convinced his guilt.(fill preposition)

Start each sentence like these:

1. Ram said that ...
2. A letter ...
3. The Taj ...

4. Think about verb tenses: present, past, future. Find the main verb and let me know what its tense is. Write the verb (feel) in the same tense.

5. ... convinced ___ his guilt.
What preposition make sense in that blank?
http://grammar.ccc.commnet.edu/grammar/preposition_list.htm

can I write

By whom was the Taj built? for 3) sentence

1) The correct answer would be: Ram told me that he goes to school daily. To change the direct speech to indirect speech, you need to follow these steps:

- Identify the reporting verb, which in this case is "said."
- Change the reporting verb to the appropriate reporting verb for indirect speech, which is usually "told."
- Change the pronouns accordingly. In this case, "me" becomes "me" in the indirect speech.
- Change the tense of the verb in the reported speech to fit the reporting verb's tense. In this case, "go" becomes "goes" to match the tense of "said."
- Optionally, you can also change the adverbs of time and place if necessary. In this case, "daily" remains the same.

2) The correct answer would be: A letter was written to me. To change the sentence to the passive voice, follow these steps:
- Identify the subject, verb, and object.
- Move the object to become the subject of the passive sentence.
- Use the appropriate form of the verb "to be" (in this case, "was") + past participle form of the main verb ("written").
- Keep the preposition "to" before the new subject (which was the original object in the active voice sentence).

3) The correct answer would be: By whom was the Taj built? To change the sentence to the passive voice, follow these steps:
- Identify the subject, verb, and object.
- Move the object to become the subject of the passive sentence.
- Use the appropriate form of the verb "to be" (in this case, "was") + past participle form of the main verb ("built").
- Start the sentence with "By whom" to indicate the doer of the action in the passive voice.

4) The correct answer would be: When we felt safe, we stopped to rest. This sentence seems to be already in the correct form. If there is any mistake that you need to clarify or change in this sentence, please provide more details.

5) The correct answer would be: The judge was convinced of his guilt. In this case, the preposition "of" is used after the verb "convinced" to show what the judge was convinced about.